In activity involving paints and varnishes, widespread use is made of diisocyanates, especially alkylene diisocyanates (Tolonate) and their derivatives of biuret type or their trimers.
However, two problems remain unsolved at present, namely:
the use of organic solvent, the presence of which is believed to be toxic and detrimental to the environment; PA1 the need to market nonvolatile products, which has led to making the molecules heavier, this being done by oligomerizing the diisocyanates; PA1 where the R.sub.1, R.sub.2 and R.sub.3, which are similar or different, denote a hydrogen or a group chosen from: PA1 either the polyfunctional compound (which advantageously comprises more than two and not more than 4 functional groups, preferably three) will initially comprise at least one group EQU [(R.sub.1)(R.sub.2)C.dbd.C(R.sub.3)--CO--Y--L'Y'-- PA1 or a compound of the type EQU [(R.sub.1)(R.sub.2)C.dbd.C(R.sub.3)--CO--Y--L'Y'--H PA1 will be reacted subsequently with the isocyanate functional groups. PA1 A) protection of a proportion (in the ratio p/n) of the isocyanate functional groups, PA1 B) reaction of the remainder of the isocyanates with a reactant referred to as "containing mobile H", of formula EQU (R.sub.1)(R.sub.2)C.dbd.C(R.sub.3)--CO--Y--L'--Y'--H PA1 or by reversing the two stages, mutatis mutandis: PA1 ethylenic monomers of isoprene, 1,3-butadiene, vinylidene chloride or acrylonitrile type, PA1 vinylaromatic monomers such as styrene, bromostyrene, alpha-methylstyrene, ethylstyrene, vinyltoluene, chlorostyrene or vinylnaphthalene, PA1 alkenoic acids, esters or anhydrides such as acrylic and methacrylic acids, alkyl acrylates and methacrylates in which the alkyl group has 3 to 10 carbon atoms, hydroxyalkyl acrylates and esters of ethylenic acids containing 4 or 5 carbon atoms. PA1 the introduction, during the polymerization of the monomer(s) forming the latex particles, of a monomer according to the invention in suspension in a proportion of the, or of one of the, monomers, and PA1 overpolymerization (in the sense of an epipolymerization), which consists of a synthesis of the type sometimes referred to as "core-shell":
this solution is not satisfactory because it employs an intricate, and hence expensive, functional group to solve the problem.